Therapeutic agents are often delivered directly to target sites of diseased tissue in various contemporary medical procedures. This direct delivery has proven to be an advantageous approach when treating numerous medical conditions. Advantages of this procedure are that only the target site may be exposed to the therapeutic and a controlled dose of therapeutic may be directly delivered to the target tissue.
Despite the advantages of direct delivery, one pronounced disadvantage is that the low viscosity of the therapeutic may result in the therapeutic being ejected or squeezed back through its point of entry in the target tissue. This problem is exacerbated in situations where the therapeutic is injected into an actively contracting tissue such as the myocardium of the heart. In such a case, the low-viscosity therapeutic may be ejected or squeezed out through its point of entry by the repeated expansion and contraction of the heart muscle. This unintended and unwanted leakage can result in an unascertainable dosage of the therapeutic being ultimately received by the target site and arbitrary and unwanted interaction between leaked therapeutic and neighboring tissue and muscle.
As such, it is advantageous for a therapeutic to have a high solid content to retard its ejection from a target site. A therapeutic with a high solid to fluid ratio, however, may resist passage through a delivery lumen thereby necessitating the use of a solvent to provide an operative balance of solids to fluids. In these cases, however, the solvent employed may be toxic in relation to the target site or incompatible with the therapeutic.
There is, therefore, a need in the art for a method and apparatus that provides efficient direct delivery of a therapeutic to a target site while allowing for easy passage through a delivery lumen of a delivery device.